Peripheral Mechanisms of Hearing consists of a series of projects that seek to establish the relationship between the sound-induced vibrations of the basilar membrane of the mammalian inner ear and their neural correlates, the trains of electrical impulses that travel along the fibers of the auditory nerve. Most of the proposed projects will be carried out in chinchillas and will study the mechanical origin of frequency-specific nonlinearities of auditory-nerve responses to sound. Basilar-membrane responses to single tones, clicks or two-tone stimuli will be recorded at either basal or apical cochlear regions by means of laser velocimetry, a method that allows detection of submicroscopic vibrations. Responses to the same stimuli will be recorded from single neurons of the auditory-nerve using microelectrodes. Other projects will determine whether the chinchilla basilar membrane responses to tones contain DC, as well as vibratory, components, and will describe the early maturation of basilar membrane vibrations in an altricial (i.e., late-maturing) rodent, the Mongolian gerbil. Results of the proposed investigations will be valuable in understanding the framework of normal mechanical-to-neural transduction in the human ear, which the ears of chinchillas and gerbils resemble. Results will also be important in specifying possible mechanical aspects of pathology in human deafness.